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XMS5 - What Temperature Sensor To Use | Application Note : AN 7


Perfect Power Application Notes.


Application Note - AN 7

This note describes the use of a engine temperature sensor with the XMS5 system, and how to adapt an existing temperature sensor to the XMS5.



The engine temperature is important, and apart from the ECU measuring it, it is very often displayed on the dashboard. It would be nice if the existing, or any other sensor, could be used with the XMS5.



The XMS5 system requires a NEGATIVE TEMPERATURE COEFFICIENT (NTC) sensor. Most engine use it. A NTC reduces its resistance as the temperature rises. This can be measured on the workbench with a multimeter, reading its resistance at room and at some elevated temperature. The resistance at the HIGH temperature must be SMALLER.
If the temperature sensor is not connected to any other device, then the sensor needs a "PULLUP". This is done internally in the XMS5 range.

XMS5 Stand Alone Unit - Engine Temperature Sensor Wiring




The XMS5 can be calibrated to read the engine temperature in DEGREE C or F. The process is described in a different application note. In short, it requires a TWO POINT calibration, which tells the XMS5 :

  • If it is a high or low point you are specifying.
  • At what step of the XMS5 temperature scale the point it
  • The display temperature (C or F) at this point.




With the above provisions, any sensor can be used, and calibrated! The practical calibration is explained in another application note.